Earth’s Geological History and the Rise of Human Civilization
The Earth was formed about 4.5 billion years ago, and humans only appeared about 5 million years ago. Much of the Earth’s past was formed without human presence. The study of the Earth’s past geological time is distinguished from historical time by the emergence of human beings.
To study the planet’s geological time, it has been divided into eras, which are subdivided into periods.
Much of the knowledge we have of the geological ages has been obtained from fossils. Fossils are organic remains, such as droppings or structures of living things, that are mineralized in the formation of sedimentary rock. The form and structure of a fossil may indicate the characteristics of the environment in which it lived.
Precambrian Era
During the Precambrian Era, the Earth was formed. There was intense volcanic activity, and the first living organisms emerged, including bacteria, eukaryotic cells, multicellular algae, and soft-bodied animals. Photosynthesis began. Following the drop in temperatures, rocks were formed, creating the Earth’s crust. There are indications that there were three continents in the Northern Hemisphere and two in the Southern Hemisphere, which collided and formed Pangea. The weather had been cold and wet.
Paleozoic Era
In the Paleozoic Era, multicellular algae diversified, and ferns originated. There was a spread of invertebrates, and the first fishes, mollusks, amphibians, and reptiles appeared. Many of these became extinct in the same era. Pangea began to fragment, forming three continents in the Northern Hemisphere and one in the South. The climate was more variable, with warm and temperate periods interspersed with glacial periods.
Mesozoic Era
The Mesozoic Era had a mild climate and abundant vegetation. New species of animals and plants emerged, including reptiles, aquatic, and terrestrial animals. This was the era of the dinosaurs. Pangea fragmented again into two continents: Laurasia in the north and Gondwana in the south. Gondwana later separated, and India moved towards the north. Laurasia fragmented into Eurasia and North America, separated by the Atlantic Ocean. In the south, South America, Africa, Australia, India, and Arabia were formed. Many groups of living things, including dinosaurs, became extinct. The first fossil mammals date to the end of this period.
Cenozoic Era
In the Cenozoic Era, mammals dominated. Mountains were formed, and the temperature changed, with intense cold periods. The Quaternary glaciations occurred, which is when the human species developed and reached its current characteristics. The continents continued to separate to where they are today. There was global warming. At the end of the Tertiary period, a gradual cooling began that culminated in glaciation. Birds and mammals, such as the mammoth, expanded to occupy all habitats. The remains of the first modern humans date to the late Tertiary, some 4 million years ago.
Social Sciences
Social sciences study human society and social relationships.
- History: The development of societies in time and space.
- Geography: Environmental processes and phenomena in interaction with humans, describing the planet.
- Physical Geography: Studies continents, the atmosphere, and ocean mass.
- Human Geography: Studies humans on the planet, including geography, economics, and politics.
- Mathematical Geography: Studies the forms and dimensions of the planet, its movements, topography, surveying, and cosmography.
- Economics: Allocates resources to satisfy needs.
- Political Science: Studies the ways of organizing society.
- Anthropology: Studies the dynamics between human groups.
- Sociology: Studies the relationships between human groups.
- Archaeology: Studies the remnants of various cultures to rebuild their lives in the past.
- Philosophy: Studies the development of human thought.
- Psychology: Studies the development of human emotions.
One of the main differences between human beings and animals is that humans can transmit their knowledge from generation to generation.
Historical Periods
Historical periods are created by scholars who lived in eras after the events they are studying. They are based on information provided by historical sources.
Paleolithic Era (Before 10,000 BCE)
This era saw the first human ancestors, humanization, and the populating of the planet. There was cultural and biological development, mastery of fire, early tools, hunting, and gathering.
Neolithic Era (10,000 BCE – 3000 BCE)
This era saw the birth of agriculture and livestock, sedentary lifestyles, the use of metals, and the birth of writing in the Near East.
Ancient History (3000 BCE – 476 CE)
This era saw the great civilizations of the East, including Egyptian, Assyrian, and Persian, and the Mediterranean, including Greek and Roman. Monarchies of divine origin were common. In Greece and Rome, republican forms of government and democracy emerged. Philosophy and classical art flourished. Latin spread in Europe, and Christianity grew and spread.
Middle Ages (476 CE – 1492 CE)
This era saw the fall of the Western Roman Empire, the development of feudalism, and the Catholic Church dominating social and spiritual life. Islam was born and expanded. The Moors were expelled from Spain, and America was discovered.
Early Modern Era (1492 CE – 1789 CE)
This era saw the first circumnavigation of the world and the rise of the Spanish and Portuguese empires. The Protestant Reformation began, leading to wars of religion. Absolute monarchies were common. Renaissance humanism and the Enlightenment spread. The French Revolution occurred.
Modern Era (1789 CE – Present)
This era saw the Industrial Revolution, the growth of cities and the world population, and the decline of monarchies in favor of parliamentary democracies. Citizens’ rights were established. Religion declined. Modern ideologies, such as liberalism, socialism, and nationalism, emerged. European empires expanded in Asia and Africa. There was much scientific and technological development. World wars, genocides, the Cold War, decolonization, space exploration, and the information revolution occurred.